Any antenna mounted outside is a candidate for a lightning strike. Furthermore, the lightning will travel down the coax cable and destroy everything on its way to ground. Without one of these, you run the risk of destroying not only the device at the end of your antenna coax, but also many devices beyond (e.g. PCs, LAN cabling, HUBs, etc).

Where does it go? The surge protector should be mounted at the entry point to your house - on the outside of the building - using a secure grounding connection. The easiest way to do this is to install a large metal (preferably copper) enclosure as a bulkhead and grounding block. This bulkhead serves as your last line of defense by keeping the lightning energy from entering your home, so it's critical that it be installed properly.

Picture is for illustration only. The unit provided is rated to 350VDC, but otherwise physically identical.

Specifications

Connector 1	N-type male
Connector 2	N-type female
Characteristic impedance	50 ohm
Frequency range	0 - 3 GHz
VSWR	< 1.5
Insertion loss	<= 0.2 dB
Discharge voltage	350 VDC